The present invention relates to a glass substrate that is useful in an information recording medium, such as a magnetic disc, a magnetic optical disc, and an optical disc, for an information recording device, such as a hard disc drive, and a process for manufacturing the same. More specifically, the present invention relates to a glass substrate for an information recording medium formed with a plurality of textures on a surface thereof and a process for manufacturing the same.
Conventionally, a magnetic disc, which is one type of an information recording medium, is manufactured by superimposing a magnetic film on the surface of a disc-shaped glass substrate. The glass substrate is subjected to an abrasion process to smooth its surface and enable high-density and large-volume recording required for the magnetic disc. A head for reading information is more easily adhered to the magnetic disc when the surface is smoothly polished. To reduce such adherence, a texture processing is performed to form an appropriate amount of protuberances, or a texture, on the surface of the glass substrate (e.g., Japanese Laid-Open Patent Publication No. 2002-117532).
Typical conventional methods for processing a texture includes a chemical texture formation method and a mechanical texture formation method. The chemical texture formation method is a method for forming a texture by etching the glass substrate by, for example, immersing the glass substrate in an etchant containing aqueous acids and alkaline aqueous solutions. The mechanical texture formation method is a method for forming a texture by supplying an abrasive slurry to the surface of the glass substrate while slidably contacting an abrasive tape thereto using a texture machine.
Comparing the chemical texture formation method and the mechanical texture formation method, the chemical texture formation method has an advantage over the mechanical texture formation method in that the formation of the texture is more easily carried out. On the other hand, in the chemical texture formation method, in the technique for immersing the glass substrate into the etchant, the formation of a texture while accurately controlling the shape of the texture is extremely difficult. Particularly, to achieve high-density and large-volume recording, the texture must have a uniform shape and be evenly dispersed over the entire surface of the glass substrate. Further, the mechanical texture formation method is more advantageous than the chemical texture formation method in accurately controlling the shape of the texture.
However, the mechanical texture formation method is more likely to form burrs, which are projections having an abnormal height, on the texture than the chemical texture formation method, and thus has a problem in that the shape of the texture tends to be uneven due to such burrs. That is, in the case of the chemical texture formation method, the surface of the glass substrate is, theoretically, evenly etched and thus burrs are less likely to be formed. On the other hand, in the mechanical texture formation method, the burrs tend to be formed by stress applied to the surface or non-scraped sections when scraping the surface of the glass substrate with the abrasive slurry. Therefore, in the mechanical texture formation method, the formation of burrs is an important issue.
The present invention focuses on the problems existing in the prior art. It is an object of the present invention to provide a glass substrate for an information recording medium capable of suppressing the formation of burrs on a texture and a process for manufacturing the same.